Re: [PATCH 3/4] arm64: dts: imx8mp-kontron: Fix boot order for PMIC and RTC

[Frank Li]

On Wed, Feb 18, 2026 at 02:25:07PM +0100, Frieder Schrempf wrote:
> From: Annette Kobou <annette.kobou@xxxxxxxxxx>
>
> The PMIC provides a level-shifter for the I2C lines to the RTC.
> As the level shifter needs to be enabled before the RTC can be
> accessed, we need to make sure that the PMIC driver is probed
> first.
>
> As the PMIC also provides the supply voltage for the RTC through
> the 3.3V regulator, we can simply express this in the DT to
> create the required dependency.
>
> This fixes sporadic boot hangs that occurred when the RTC was
> accessed before the level-shifter was enabled.
>
> Fixes: 946ab10e3f40f ("arm64: dts: Add support for Kontron OSM-S i.MX8MP SoM and BL carrier board")
> Signed-off-by: Annette Kobou <annette.kobou@xxxxxxxxxx>
> Signed-off-by: Frieder Schrempf <frieder.schrempf@xxxxxxxxxx>
> ---
>  arch/arm64/boot/dts/freescale/imx8mp-kontron-osm-s.dtsi | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/arch/arm64/boot/dts/freescale/imx8mp-kontron-osm-s.dtsi b/arch/arm64/boot/dts/freescale/imx8mp-kontron-osm-s.dtsi
> index b97bfeb1c30f8..bc1a261bb000e 100644
> --- a/arch/arm64/boot/dts/freescale/imx8mp-kontron-osm-s.dtsi
> +++ b/arch/arm64/boot/dts/freescale/imx8mp-kontron-osm-s.dtsi
> @@ -330,6 +330,12 @@ rv3028: rtc@52 {
>  		pinctrl-names = "default";
>  		pinctrl-0 = <&pinctrl_rtc>;
>  		interrupts-extended = <&gpio3 24 IRQ_TYPE_LEVEL_LOW>;
> +		/*
> +		 * While specifying the vdd-supply is normally not strictly necessary,
> +		 * here it also makes sure that the PMIC driver enables the level-
> +		 * shifter for the RTC before the RTC is probed.
> +		 */
> +		vdd-supply = <&reg_vdd_3v3>;

Dose reg_vdd_3v3 controller by gpio, or actually it is level shifter?

Frank
>  	};
>  };
>
> --
> 2.52.0
>